A 3rd Generation Partnership Project Long Term Evolution (Rel-8 or Rel-9) system (hereinafter, referred to as an LTE system or a Rel-8 system) adopts Multi-Carrier Modulation (MCM) in which a single Component Carrier (CC) is divided into a plurality of frequency bands. On the other hand, a 3GPP LTE-Advanced system (hereinafter, referred to as an LTE-A system or a Rel-10 system) may use Carrier Aggregation (CA) by aggregating one or more CCs to support a broader system bandwidth than in the LTE system. The term CA may be interchanged with carrier matching, multi-CC environment, or multi-carrier environment.
For a single-CC environment such as the LTE system, only multiplexing of Uplink Control Information (UCI) and data using a plurality of layers on one CC is specified.
The legacy PUCCH format 3 carries only an ACKnowledgment/Negative ACKnowledgment (ACK/NACK) and a Scheduling Request (SR) that occupy up to 20 bits and another PUCCH format carries channel quality control information (i.e., Channel Quality Indicator/Precoding Matrix Index (CQI/PMI)) of up to 11 bits.
If a User Equipment (UE) transmits CSI periodically to a Base Station (BS) in a multi-carrier (multi-cell) environment, the UE should transmit only CSI for one cell by one PUCCH transmission. Therefore, CSI is often dropped depending on a transmission scheme or an environment and thus the BS does not have accurate knowledge of a channel state. Moreover, the UE should transmit the CSI a plurality of times, thereby degrading network performance. Particularly an uplink reporting timing may be very short in Time Division Duplexing (TDD). The resulting increase in the number of collisions between CSI transmissions may lead to an increased frequency of CSI drops.